A cache of 250-million-year-old fossils rediscovered in Australia has shown a diverse community of early ocean predators following Earth's worst mass extinction. These marine amphibians, including species from the trematosaurid group, indicate a rapid global spread in the early Mesozoic era. The findings challenge previous views that limited such creatures to a single species in the southern hemisphere.
About 252 million years ago, the end-Permian mass extinction wiped out much of life on Earth, ushering in extreme global warming and the start of the Mesozoic era, known as the Age of Dinosaurs. In the aftermath, marine ecosystems began to reform, with the first sea-going tetrapods—limbed vertebrates like amphibians and reptiles—emerging as apex predators.
Fossils from this period, collected in the 1960s and 1970s from the Kimberley region in northern Western Australia, were initially analyzed in 1972 and attributed to a single species, Erythrobatrachus noonkanbahensis. These specimens, found eroding from rocks at Noonkanbah cattle station east of Derby, were divided between Australian and U.S. museums but later misplaced. An international search in 2024 finally located them, enabling reexamination with modern techniques such as high-resolution 3D scans.
The analysis, published in the Journal of Vertebrate Paleontology, reveals that the fossils represent at least two trematosaurid temnospondyls—crocodile-like relatives of modern salamanders and frogs that could grow up to 2 meters long. Erythrobatrachus had a broad-headed skull about 40 cm long, suited for larger prey, while Aphaneramma featured a long, narrow snout for catching small fish. Both inhabited the same shallow bay environments less than 1 million years after the extinction.
Erythrobatrachus appears unique to Australia, but Aphaneramma fossils have been found in contemporaneous rocks in Svalbard (Scandinavian Arctic), the Russian Far East, Pakistan, and Madagascar. This distribution points to a swift expansion of these early marine tetrapods across ancient supercontinents, filling diverse ecological niches in the planet's recovering oceans.
The rediscovered fossils are now returning to Australia, enhancing understanding of post-extinction recovery in the southern hemisphere, where such discoveries have been scarce compared to the northern hemisphere.